A temperature gauge could do it (give weapons a degree value, both for hitting armor and for firing, same for afterburners and maybe a couple other things, make it decrease at a certain rate over time if nothing new is happening, and if it gets up to the critical level your rockets start blowing up in your face when you fire them and your afterburner doesn't work (killing you because you fired up your afterburner might not work, just have a "safety" that keeps you from using it if you get too high up), and once it gets to a certain point you start losing HPs fast.
Fact, it could be set up like HPs, so that if a fighter has, say, 2500 hit points, that's 2500 degrees it can take total, with firing, say, a Prometheus adding 40 degrees, a Kayser 10, afterburners 500, a direct hit by a Prom 800, etc. , with the ship venting about 2% a second (poss. depending on your use of engines?), and once you get up to 90% stuff starts exploding.
It'd basically mean adding a whole new value to everything, and I don't know how complicated that would be, but it could be pretty cool.